In recent years, technologies used in vehicles such as cars to detect traveling surroundings outside a vehicle and recognize an obstacle and a preceding vehicle by using a vehicle-mounted camera, a laser radar device, or the like, and to perform various driving support controlling operations, such as a warning outputting operation, an automatic braking operation, and an automatic steering operation, thereby preventing collisions of vehicles and improving the safety, have been developed and put in practical use.
For example, Patent Literature 1 discloses a technology of urging the driver of a vehicle to perform a braking operation, thereby preventing collisions, by controlling a warning timing in accordance with the degree of risk of collision with a preceding vehicle or a following vehicle.
Further, for example, Patent Literature 2 discloses a technology of controlling a warning timing in accordance with the speed at which the brake pedal of a driver's vehicle is stepped on, and, when detecting a following vehicle, and advancing the timing at which a warning is presented, thereby appropriately preventing an excessive approach of the following vehicle which results from the braking control on the driver's vehicle.
Further, for example, Patent Literature 3 discloses a technology of comparing a driver's specific spare time for operation with time-to-collision, and, when the time-to-collision is less than the driver's specific spare time for operation, determining that the driver's state is not a normal state, and outputting a warning.